The present invention relates to a temperature control system for a sheet support plate of a printer which has at least two power supplies for powering different sub-systems of the printer, the temperature control system including at least one heater.
In the copying and printing industry, a temperature controlled sheet support plate is frequently used for supporting an image receiving sheet and at the same time controlling the temperature thereof. For example, in a hot melt ink jet printer, a sheet, e.g. a sheet of paper, is advanced over the sheet support plate while the image is being printed. At room temperature, the hot melt ink is solid, and it is therefore necessary that the ink is heated in the printer above its melting point, before it can be jetted onto the paper. The ink droplets that have been jetted onto the paper tend to spread-out more or less before the ink solidifies. In order to obtain a suitable and constant amount of spreading of the ink droplets, the temperature of the sheet support plate and hence the temperature of the paper should be controlled such that the ink cools down at an appropriate rate.
In an initial phase of the print process, when a new sheet has been supplied, it is generally desirable to heat the sheet and to keep it at a suitable operating temperature. Thus, the sheet support plate should be heated by a heater. However, in the further course of the print process, it is necessary to dissipate the heat of the ink that solidifies on the paper. To that end, a temperature control fluid, e.g. a liquid, may be passed through a cavity in the plate in order to control the temperature of the plate.
For reasons of power consumption, it is required that the printer enters into a so-called sleep mode, when the printer is not operating for a certain amount of time, and in the sleep mode, among others, the heating system for the sheet support plate is switched off. Thus, when the printer is switched on or is switched from the sleep mode into the operating mode again, it will take a certain amount of time for the sheet support plate to be heated to its operating temperature. In order to shorten this warming-up process of the sheet support plate, a considerable amount of heating power is required.